A substantial proportion of these infants received prolonged antibiotics despite their lower a priori risk.

Premature infants who were delivered by cesarean section, had membrane rupture at delivery, and in whom there was no maternal clinical chorioamnionitis were at a low risk for early-onset sepsis, according to the results of a study published in Pediatrics.

To determine the impact of delivery characteristics on the risk for early-onset sepsis, outcomes for 15,433 infants born between 22 and 28 weeks of gestation were evaluated. The rates of early-onset sepsis, mortality, and morbidity were compared between infants who were hypothesized to be low risk (n=5759, 37%) and those who were not low risk (n=9674, 63%). Low-risk infants were considered to have all of the following delivery characteristics: cesarean delivery, membrane rupture at delivery, and no maternal clinical chorioamnionitis.

Infants classified as low risk had a lower rate of mortality within the first 12 hours after birth compared with other infants (2.1% vs 12.9%). Moreover, the low-risk group had a lower rate of the composite outcome of mortality within 12 hours and early-onset sepsis (2.6% vs 15.1%; adjusted RR 0.36; 95% CI, 0.30-0.43).

Fewer infants in the low-risk group who survived more than 12 hours received antibiotics compared with the non-low-risk group (34.1% vs 47.4%, P <.001).

The study authors noted that “delivery characteristics of infants born at 22 to 28 weeks [gestational age] were useful in identifying those with significantly lower risk of [early-onset sepsis]....Recognition of differential [early-onset sepsis] risk may help guide early empirical antibiotic use among approximately one-third of extremely preterm infants.”